This invention relates to an electromagnetic relay and, more particularly, to a seesaw type electromagnetic relay serving as a continuous contact.
A seesaw type electromagnetic relay of the type is disclosed as prior art in Japanese Unexamined Patent Prepublication of Tokkai No. Hei 3-222,230, namely, 222,230/1991. According to Tokkai No. Hei 3 222,230, the seesaw type electromagnetic relay is symmetrical in shape for an armature. The armature comprises a central part rotatably supported on a supporting point and a pair of armature arm parts which extends from the central part in opposite directions. The armature makes a seesaw motion by excitation of an electromagnet. The armature is supported by a supporting member at the central part. The seesaw type electromagnetic relay comprises a pair of movable springs which extend to a direction in parallel with the armature with spaces left therebetween. Each movable spring comprises a middle part fixed to the supporting member and a pair of spring sections extending in parallel with both armature arm parts. The middle part of the movable spring is always in electrically contact with a common contact.
Each spring section forks into two branches to form a pair of spring pieces. The spring pieces have two free end parts on which two movable contact elements are mounted. The two movable contact elements are collectively called a twin movable contact. Each twin movable contacts faces a fixed contact. For each movable spring, a set of one twin movable contact and one fixed contact serves as a make contact while another set of another twin movable contact and another fixed contact acts as a break contact.
The seesaw type electromagnetic relay is operable as either a transfer contact or a continuous contact. The transfer contact is a contact where the break contact opens before the make contact closes. The continuous contact is a contact where the make contact closes before the break contact opens. The continuous contact is also called a make-before-break contact.
In a case of making the conventional seesaw type electromagnetic relay operable as the continuous contact, both spring sections in each movable spring are bent downward. As a result, the seesaw type electromagnetic relay has stronger maximum load force and it results in requiring large load energy upon driving of the continuous contact. As a result, there is little margin for a matching between magnetic attraction force of the electromagnet and urging force of an urging spring. In addition, the conventional seesaw type electromagnetic relay serving as the continuous relay consumes large power upon driving of it.
Various other electromagnetic relays have already proposed in, for example, Japanese Unexamined Utility Model Prepublication or Jikkai Nos. Sho 60-168,243, Hei 2-18,246, and Hei 4-78,720. Those Prepublications disclose the electromagnetic relays where a distance between an movable contact element of a twin movable contact and a fixed contact is different from a distance between another movable contact element of the twin movable contact and the fixed contact. However, all of the Prepublications only disclose the electromagnetic relays each of which acts as the make contact.